This invention relates to an audio data reproducing device for a motion picture film and a clock generating device in a changeover system for a motion picture film conveniently provided in the audio data reproducing device. More particularly, it relates to such audio data reproducing device and the clock generating device in the changeover system for a motion picture film in which the former half and the latter half of the motion picture are respectively recorded in a first roll and a second roll and reproduction is performed through the first and second rolls continuously with changeover between the first and the second rolls.
With a conventional motion picture film, picture recording regions are arrayed in the form of frames at a mid portion of the film, and perforations for taking up the film are provided in rows on both sides of the picture recording regions. An analog sound track is provided in a straight line between the picture recording regions and one of the rows of the perforations extending along the film takeup direction. It is on this analog sound track that audio signals are recorded in an analog form.
Recently, with the progress in digital techniques, attempts are being made for digitally recording the audio information. Since the recording positions for the picture recording regions and the analog sound tracks are standardized by the Society of Motion Picture and Television Engineers (SMPT), the digitized audio information (audio data) are recorded in positions other than the recording positions for the picture recording regions or the analog sound track.
Specifically, audio data for the right channel and audio data for the left channel are formed as the audio data which are recorded in straight lines in each digital sound track provided along the proceeding direction of the motion picture film between the rows of the perforations and the film edges.
The audio data recorded in the digital sound tracks are made up of synchronization data, audio data and tracking patterns recorded in a direction normal to the film proceeding direction. The synchronization data is recorded at the leading end of a block made up of a pre-set number of data units, and the audio data is recorded next to the synchronization data on the block basis. The track pattern is recorded at the recording start portion and at the recording end portion. On the whole, the tracking patterns are recorded in bands along the film proceeding direction on both sides of the digital sound tracks.
The reproducing apparatus for the motion picture film for reproducing the audio data from such motion picture film reads out the audio data etc. of each channel by two CCD line sensors provided for scanning the digital sound tracks of the motion picture film. Each CCD line sensor has a one-line read-out area provided for extending in a direction at right angles to the film proceeding direction. During reproduction, the light radiated from a continually lighted halogen lamp is radiated as a playback light on each readout area via the digital sound tracks of the motion picture film. On the readout region of the CCD line sensor, the synchronization data, audio data or the tracking pattern recorded on the digital sound tracks are illuminated as corresponding lighted data or pattern.
The CCD line sensor receives the lighted synchronization data, audio data and the tracking pattern and, responsive to the readout pulse, converts them into electrical signals which are transmitted to a data processor. The data processor reproduces the audio data block-by-block, in synchronism with the synchronization data, and transmits the reproduced data to a D/A converter. The D/A converter converts the audio data into analog signals which are routed to a speaker unit. Thus an audio output corresponding to the audio data is produced via the speaker unit.
The data processor detects the tracking pattern from the CCD line sensor by way of performing tracking control. The tracking pattern is recorded at the recording start position and the recording end position for one-line audio data. The data processor detects the level difference, for example, of the tracking pattern reproduced at the recording start position and the tracking pattern reproduced at the recording end position for detecting the tracking error and variably controls the readout timing by the CCD line sensor in accordance with the detected tracking error.
Thus it is possible with the data processor to correct the tracking error in order to reproduce audio data at all times under a just-track condition.
Next, if a given motion picture is separately recorded on two rolls, that is a first roll and a second roll, and the reproducing operation is to be shifted from the first roll to the second roll by way of a so-called changeover operation, it is necessary to carry out the operation smoothly lest there should occur interruption of the picture or sound.
The conventional reproducing apparatus for a motion picture film has two reproducing systems, namely a first reproducing system and a second reproducing system, and the first and second reproducing systems are respectively set on the first and second rolls. When the first roll reproduced by the first reproducing systems approaches its end, the second roll starts to be reproduced by the second reproducing.
It is noted that the film perforations are repeatedly formed at a frequency of, for example, 96 Hz. Each reproducing system detects the perforations for forming a detection output having the frequency of 96 Hz. The detection output is stabilized by phase locking with a phase locked loop (PLL) and the system clocks of a pre-set frequency are formed based upon the detection output. These system clocks are utilized in reproducing the audio data.
In the playback start portion of the second roll, there is recorded the same information as the audio data and the picture information recorded for a pre-set time duration in the terminal portion of the first roll. When the playback end of the first roll is approached, the second reproducing system starts its reproducing operation. Thus the first and second reproducing systems are run in parallel and the picture information and audio data reproduced by the first reproducing system are changed over at a measured timing with respect to the picture information and audio data reproduced by the second reproducing system. This achieves the changeover operation, that is the picture information and audio data reproduced by the first reproducing system are changed over to the picture information and audio data reproduced by the second reproducing system.
It is noted that each reproducing system runs the motion picture film under a moderate tension for reproduction. This tension, however, becomes labile at the start and towards the close of roll winding. Consequently, such tension becomes extremely labile during the changeover operation carried out at the start and towards the close of roll winding.
Since each reproducing system forms system clocks based upon the detection output of the film perforations, if the tension becomes extremely labile, the output of detection of the perforations cannot be phase-locked by the PLL circuit. On the other hand, since the audio data is reproduced with the labile system clocks produced under such conditions, correct audio data cannot be reproduced.
Thus the conventional motion picture film reproducing device has a drawback that ideal changeover is obstructed.